Also called a dropper program or a virus dropper, a program that when run will install a virus, Trojan horse or worm onto a hard drive, floppy disk or other memorymedia. The dropper itself is not a virus �� it does not replicate; instead, it��s more like a Trojan horse in that it carries the malicious code with it and is not detected by virus-scanning software because it is not an infected file but carries the code to "drop" a virus into a system. Droppers are uncommon.